JP2002217451A - Light-emitting diode and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting diode which enables the upper face and the side face of a semiconductor chip to be made uneven and a thin film to be formed on the uneven faces, without the need for protecting electrode, improving the light extraction efficiency, and uses a p-type region as an upper face, and also to provide a method of manufacturing the same. SOLUTION: The light-emitting diode comprises a pn junction, having the p-type region 13 formed on the upper side. By forming unevenness 17 and a thin film 18 on the upper face and the side face of the semiconductor chip, the light-emitting diode, having high external light extraction efficiency, can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a light emitting diode having a pn junction structure in which an upper surface is formed of a p-type region. The present invention relates to the manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in such a light emitting diode, a plurality of semiconductor regions are stacked on a semiconductor substrate by, for example, epitaxial growth to form a p-type first semiconductor region and an n-type second semiconductor region. A plurality of light-emitting diode chips comprising at least one pn junction and having a GaAs or GaAlAs-based p-type region disposed on the upper surface, and forming electrodes on the upper and lower surfaces of the semiconductor chip. It is manufactured by cutting a substrate and separating each of the semiconductor chips.

According to the light emitting diode having such a configuration, by applying a drive voltage between the electrodes, a voltage is applied between the p-type first semiconductor region and the n-type second semiconductor region. Light is emitted from the pn junction, and the light is emitted to the outside through the upper p-type region.

In the light emitting diode having such a configuration, the refractive index of the semiconductor constituting the p-type region is approximately 3, which is largely different from the refractive index of air of 1. For this reason, due to such a difference in the refractive index, the light emitted from the pn junction at the interface with the air in the p-type region, only the light having a limited incident angle is emitted to the outside, and the remaining light is emitted. Is reflected at this interface and is absorbed inside the p-type region and the n-type region, so that there is a problem that the light extraction efficiency is reduced. Therefore, in order to increase the light extraction efficiency of the light emitting diode, the surface of the semiconductor chip is made uneven to increase the probability that the light emitted from the pn junction has an incident angle at which the light can be emitted to the outside on the semiconductor chip surface, and It is known that it is effective to form a thin film having a specific refractive index and a specific thickness on the surface of a semiconductor chip to lower the reflectance.

In the conventional method, taking the case of a GaAlAs light emitting diode as an example, before separating the semiconductor chip, the electrodes in the p-type region are protected by a mask or the like, and the surface is made uneven by, for example, 95: 5 nitric acid: sulfuric acid. And then
A thin film having a specific refractive index has been formed by depositing or sputtering a composition other than the semiconductor component of the semiconductor chip having a specific refractive index, for example, silicon nitride, silicon oxide, or the like.

[0006]

However, in the conventional method of manufacturing a light emitting diode having a roughened surface and a thin film, it is necessary to protect the electrodes by using a mask or the like when the roughened surface is formed. After the above process, it is necessary to remove a mask and the like for protecting the electrodes, so that the process is complicated and the cost is increased. Further, since the steps of forming the irregularities and forming the thin film are separate steps, the number of steps is increased and the processing time is increased, which also causes an increase in cost. Further, after the formation of the unevenness and the formation of the thin film, it is necessary to perform a separation operation of the semiconductor chip.
The light extraction efficiency is not sufficiently improved.

For this reason, a method of forming unevenness and forming a thin film after separation of a semiconductor chip can be considered.
It is necessary to attach and remove an electrode protection material such as a mask for protecting the electrodes, and the operation becomes complicated.

In a light emitting diode comprising a pn junction having an n-type region disposed above, the use of a 15-80% aqueous nitric acid solution enables the n-type region to be made uneven without protecting the electrodes. Therefore, after separation of the semiconductor chip, unevenness and thin film formation are performed without an electrode protection material, and at this time, an arsenic compound mainly composed of arsenic hydroxide generated from As dissolved in an aqueous nitric acid solution is deposited on the uneven surface. A light-emitting diode having a sufficient light extraction efficiency has been obtained by a simple process of forming a thin film having a specific refractive index by the present inventors (Japanese Patent Application No. 11-131, filed by the present inventors).
-203397). However, in the case of a light-emitting diode in which the light extraction surface is a p-type region, the use of the same processing solution causes the surface of the semiconductor chip, which is the p-type region, to be dissolved by the processing solution, so that the uneven shape is not formed Or, there was a problem that the electrode was peeled off. Thus, there was no treatment liquid that could form an uneven shape in the p-type region and did not damage the electrode.
For this reason, the light-emitting diode having a pn junction structure in which the upper surface is formed of a p-type region, the light-emitting surface is made uneven, and a thin film is formed on the uneven surface to increase the light extraction efficiency is described above. However, there is a problem that the cost is high because the manufacturing is performed by the conventional method described above.

In view of the above problems, the present invention provides a light emitting diode having a high light extraction efficiency even in a light emitting diode in which a p-type region is arranged above, and a method of manufacturing a light emitting diode which can be manufactured at low cost. It is intended to provide.

[0010]

In order to solve the above-mentioned problems, the present invention provides a semiconductor chip in which a p-type first semiconductor region and an n-type second semiconductor region are arranged so as to form a pn junction. And an electrode disposed in at least a p-type region of the semiconductor chip, configured to extract light from a region and a side surface other than the electrode on the upper surface of the semiconductor chip, And / or a light-emitting diode in which a side surface has an uneven surface of about 0.5 to 5 μm and a thin film of a compound containing a semiconductor chip material is adhered to at least the uneven surface, wherein the semiconductor chip has a p-type first surface. And the semiconductor chip is configured such that the side surfaces of the semiconductor chip are a p-type first semiconductor region and an n-type second semiconductor region. Thereby, the light emitting surface has unevenness, and has a thin film on the uneven surface,
A light emitting diode having high light extraction efficiency is provided.

In the present invention, the p-type first semiconductor region and the n-type second semiconductor region are preferably formed of a GaAs-based or GaAlAs-based semiconductor material. In the present invention, preferably, at least the p-type first semiconductor region is provided with a slope change region having an uneven surface at a side edge thereof. The thin film is preferably an arsenic compound containing arsenic hydroxide as a main component.

According to this structure, since the top and side surfaces of the semiconductor chip have irregularities, light emitted from the pn junction can be extracted out of the semiconductor chip with high efficiency. Since the thin film of the compound containing the chip material is attached, light emitted from the pn junction can be extracted out of the semiconductor chip with high efficiency. That is, a light emitting diode with high luminous efficiency, in which the upper surface of the semiconductor chip is the p-type first semiconductor region and the lower surface of the semiconductor chip is the n-type second semiconductor region, is obtained. This light emitting diode can be effectively used, for example, when the n-type semiconductor region of the light emitting diode must be face-down bonded on a wiring pattern on a wiring board.

Further, according to the present invention, a plurality of semiconductor regions are stacked on a semiconductor substrate and arranged so that at least the n-type second semiconductor region and the p-type first semiconductor region form a pn junction. A first step of forming a plurality of semiconductor chips provided; a second step of forming electrodes in at least a p-type region of the semiconductor chip; And a third step of adhering a thin film of a compound containing a semiconductor chip material to the uneven surface. And the side surfaces are treated with a treatment solution comprising nitric acid and a water-soluble organic solvent to make the surface uneven, and a thin film of a compound containing a semiconductor chip material is attached to the surface having the unevenness. Are, thereby without performing the electrode protection, collectively a plurality of semiconductor chips, because the unevenness of the thin film formed at the same time, it is possible to manufacture a light emitting diode according to the present invention at low cost.

In the present invention, between the second step and the third step, an adhesive tape is adhered to the back surface of the semiconductor chip, and the semiconductor chip is cut for each semiconductor chip. Elongating the tape to extend the space between the semiconductor chips; and elongating the semiconductor chip separated and extended and adhered to the adhesive tape in the third step while the tape is adhered to the adhesive tape. Can be applied.

In the present invention, the treatment liquid preferably comprises a mixture of nitric acid and methanol. Also, preferably,
The third step is performed at a processing liquid temperature of 10 ° C to 50 ° C. More preferably, the third step is performed in a processing time of 10 seconds to 5 minutes. More preferably, the mixing ratio of nitric acid and methanol in the treatment liquid is 10: 0.1 by volume.
To 5.

According to the above configuration, in the light emitting diode comprising a pn junction in which a p-type region is disposed above, a semiconductor chip is formed in the first stage and the second stage in the same manner as in the related art. In the third stage, a treatment solution comprising nitric acid and a water-soluble organic solvent is used, which does not react with the electrodes and does not dissolve the p-type region. Accordingly, in the third stage, the upper surface region and the side surface of the p-type region excluding the electrode of the semiconductor chip from which light is emitted are made uneven using the processing liquid, and the thin film is formed at the same time. And the processing time is shortened, so that the production efficiency is improved. In this case, the use of a treatment liquid that does not react with the electrode eliminates the need for protecting the electrode, that is, attaching and removing the electrode protection material. Therefore, the number of steps is reduced, and the processing time is shortened, so that the production efficiency is improved. In addition, by using a processing solution that does not dissolve the p-type region, the upper surface region and the side surface of the p-type region are reliably made uneven, so that the light extraction efficiency can be reliably improved.

Further, between the second step and the third step, an adhesive tape is adhered to the back surface of the semiconductor chip, and the semiconductor chip is cut for each semiconductor chip.
In the case of including an elongating step of extending the adhesive tape to increase the interval between the semiconductor chips, since the interval between the semiconductor chips is larger than the cutting allowance, the unevenness by the processing liquid in the third step and In forming the thin film, the processing liquid easily enters between the semiconductor chips, so that the side surface of the semiconductor chip can be made uneven and the thin film can be reliably formed. Further, since the semiconductor chip that has been separated and stretched and attached to the adhesive tape is made uneven and formed as a thin film while being attached to the adhesive tape, a plurality of semiconductor chips can be processed at once, Since the number of processes is small and the processing time is short, the production efficiency is improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 is a diagram showing an embodiment of a light emitting diode according to the present invention. In FIG. 1, a light emitting diode 10 is a pn junction light emitting diode chip, a semiconductor chip 20 formed of an n type semiconductor region 12 and a p type semiconductor region 13 disposed thereon, and Electrodes 14 and 15 provided on the upper surface and the rear surface of the semiconductor chip 20 so as to sandwich the same.

Here, the pn junction 16 formed between the n-type semiconductor region 12 and the p-type semiconductor region 13 is formed parallel to the upper and lower surfaces of the semiconductor chip 20, and The end of 16 is exposed on the side surface of the semiconductor chip. The side surface of the semiconductor chip 20 including the pn junction 16 is formed almost vertically.

The n-type semiconductor region 12 is made of, for example, Ga
For example, as an impurity, for example, T
e etc. are added. The p-type semiconductor region 13 is obtained by adding, for example, Zn or the like as an impurity to a GaAlAs-based semiconductor material, for example.
Note that any of the above GaAlAs-based semiconductor materials is Al
The mixed crystal ratio is about 0 to 0.8. Here, the n-type semiconductor region 12 and the p-type semiconductor region 13 form a pn junction 16 at the boundary therebetween. The n-type semiconductor region 12 and the p-type semiconductor region 1
Numeral 3 is formed by successively laminating, for example, by epitaxial growth on, for example, an (100) plane of a semiconductor substrate (not shown), so that the (100) plane coincides with the surface orientation.

Further, on the surface (upper surface) side of the light emitting diode 10, the semiconductor chip 20 except the electrode 15 is formed.
The upper surface and the side surfaces of the semiconductor material are subjected to a roughening process to form a rough surface 17, on which a thin film 18 mainly containing a compound containing a part of the composition of the semiconductor material, for example, arsenic hydroxide is formed. Have been.

The concavo-convex surface 17 has a concavo-convex structure formed by forming depressions on the upper surface and side surfaces of the semiconductor chip 20, and the depth of the depressions is, for example, about 0.5 to 5.0 μm. The etching is performed, for example, by a processing liquid. In addition, at least the uneven surface 1
7 a thin film 18 mainly composed of arsenic hydroxide or the like
Is a thickness of 0.01 μm or more, and the optimum value is 0.01
It has a thickness of about μm to 5 μm.

The light emitting diode 10 described above is manufactured according to the manufacturing method of the present invention as follows. FIG. 2 is a process chart showing the manufacturing method of the present invention. That is, FIG.
According to the process chart shown in FIG.
On a semiconductor substrate, an n-type semiconductor region 12 and a p-type
The semiconductor regions 13 of the mold are sequentially laminated and formed. Subsequently, in step ST2, electrodes are formed on the back surface of the n-type semiconductor region 12 from which the semiconductor substrate has been removed and on the upper surface of the p-type semiconductor region 13. FIG. 3 is a schematic sectional view of an electrode formed on a semiconductor chip. As shown in FIG. 3, electrodes 14 and 15 are patterned in the semiconductor chip area, respectively. Steps ST1 and ST2 described above are the same as the conventional method for manufacturing a light emitting diode.

Next, in step ST3, the stacked semiconductor regions 12, 13 are cut for each semiconductor chip region to separate each semiconductor chip 20. In this case, before the cutting operation, an adhesive tape 21 is attached to the electrode 14 on the back surface. Thus, the semiconductor chips 20 are not separated from each other after the cutting but are held integrally at predetermined intervals.

Thereafter, in step ST4, a so-called expanding operation is performed. FIG. 4 is a diagram showing the arrangement of the semiconductor chips after the expansion. The expansion is performed by extending the adhesive tape 21 in the vertical and horizontal directions. Thereby, the adhesive tape 21 extends in the vertical and horizontal directions, and the interval between the semiconductor chips 20 is increased. Here, the interval between the semiconductor chips 20 is set to an interval equal to or longer than the cut surface length, for example, 30 μm or more, so that the side surface of each semiconductor chip 20 can be easily made uneven in the subsequent uneven processing. .

As shown in FIG. 4, the periphery of an adhesive tape 21 to which the semiconductor chip 20 is adhered is fixed by a ring 22. The adhesive tape 21 and the ring 22 are made of a material which is not deteriorated by a processing liquid described later. I have.

Each semiconductor chip 20 is connected to a ring 22.
Each of the semiconductor chips 20 is immersed in the processing liquid, so that the upper surface and the side surface of each semiconductor chip 20 are processed to be uneven by the processing liquid. Here, a mixture of nitric acid (61% by weight) and methanol as a water-soluble organic solvent is used as the treatment liquid. The mixing ratio of nitric acid and methanol was 10: 0.
It is 1 to 5, preferably 10: 1. In addition, nitric acid 10
When the methanol is 5 or more, the reaction by the processing solution is weakened, and the processing time becomes longer. When the methanol is 0.1 or less with respect to 10 nitric acid, the surface of the semiconductor chip 20, particularly, p Since the surface of the semiconductor region 13 of the mold is dissolved, it is not possible to obtain desired unevenness and thin film formation. Further, the temperature of the processing solution is 10 ° C.
The temperature is 50 ° C., preferably 25 ° C., and the processing time is 10 seconds to 5 minutes, preferably 1 minute. The processing time is an example, and is not limited to this, and may be appropriately set, for example, between 10 seconds and 5 minutes so as to obtain desired surface roughness. Here, when the processing time is 10 seconds or less, sufficient unevenness is not performed.
If the processing time is 5 minutes or longer, excessive unevenness is caused.

As a result, the upper and side regions of each semiconductor chip 20 react with the processing liquid to be roughened, so that the uneven surface 17 is formed. At the same time, the semiconductor material dissolved in the processing liquid is removed. By reacting in the processing liquid, an arsenic compound containing arsenic hydroxide as a main component is generated. The arsenic hydroxide and the like adhere to the upper and side surfaces of each semiconductor chip 20 to form the thin film 18. afterwards,
For example, the semiconductor chips 20 are washed with water for 30 seconds to 2 minutes and dried to complete the unevenness and the thin film formation of each semiconductor chip 20, thereby completing each semiconductor chip 20 shown in FIG.

FIGS. 5 and 6 are cross-sectional electron micrographs of a light emitting diode prepared by the manufacturing method of the present invention.
As shown in the electron micrographs (1000 × and 5000 ×) shown in FIGS. 5A and 5B and FIGS. 6A and 6B, the upper surface of the semiconductor chip 20 excluding the electrodes 15. The area and side surface are made uneven, and this unevenness is about 5 μm.
high density at intervals of m to 10 μm,
The side wall is substantially perpendicular to the surface of the semiconductor chip, which indicates that the light emitted from the pn junction has an extremely high probability of having an incident angle at which light can be emitted to the outside. Further, it can be seen that the thin film 18 is formed with a uniform thickness over the entire surface of the unevenness, the reflected light is suppressed by the thin film 18, and the light is effectively extracted to the outside.

Here, an experimental example will be described below. In the third step, GaAlA having an Al mixed crystal ratio of 0 to 0.45 is used.
light emitting diode 10 made of Nitto Denko
Ring 22 made of polypropylene with 8S adhesive tape
Fix with. Then, by using a processing liquid having a mixing ratio (volume ratio) of nitric acid and methanol of 10: 1, a processing liquid temperature of 25% was used.
After performing the treatment of forming irregularities and forming a thin film at a temperature of 1 ° C. for 1 minute, the film was washed with water for 1 minute and dried.

The light emitting diode 1 thus obtained
A light emission amount of 0 was measured. FIG. 7 is a comparison diagram of the light emission amount of the light emitting diode of the present invention and the light emitting diode formed by the conventional technique. The light emission amount is the light emission amount integrated over all the light emitting directions, that is, the light amount taken out from the whole. The horizontal axis is the processing time with the processing liquid, and the vertical axis is the light emission amount ratio expressed on the basis of the light emission amount of the light emitting diode not subjected to the unevenness processing. In FIG. 7, a curve indicated by a symbol A is a light amount-processing time curve of the light emitting diode of the present invention, and a curve indicated by a symbol B is a conventional technique, that is, the electrode on the p-type region is protected by a protective material. It is a light amount-processing time curve of a light emitting diode (side surface is not subjected to unevenness processing) manufactured by performing unevenness processing and then separating into chips. As is apparent from FIG. 7, the light emitting diode of the present invention improves the light emission amount by about 20%, while the light emitting diode of the present invention improves the light emission amount by about 5%.
0% improvement in light emission is seen.

Further, according to the manufacturing method of the present invention, the roughening treatment and the formation of the thin film are carried out on all the semiconductor chips adhered on the adhesive tape at one time and in the same step with the same treatment liquid. Thus, costs can be reduced and processing time is reduced. Further, since the chemical solution for the surface roughening treatment and the formation of the thin film is a mixed solution of nitric acid and methanol, the electrodes 14 and 1 constituting the semiconductor chip 20 are formed.
Does not react with 5. Accordingly, a mask or the like for protecting the electrodes is not required, and attachment and removal of the mask and the like before and after the processing are not required, so that the operation is simplified and the cost is further reduced.

In the above-described embodiment, a treatment liquid for nitric acid and methanol is used as the treatment liquid for making the surface uneven and forming the thin film. However, the treatment liquid is not limited to this, and is not soluble in nitric acid. Organic solvents such as ethanol, acetone,
A mixture of a water-soluble organic solvent such as isopropyl alcohol may be used. In the embodiment described above,
The semiconductor materials and impurities of the p-type semiconductor region 13 and the n-type semiconductor region 12 of the light-emitting diode 10 are not limited to those illustrated, and any other semiconductor materials and impurities may be used according to the emission color of the light-emitting diode 10 and the like. Obviously, it is possible to select the type and concentration of the impurity.

[0034]

As can be understood from the above description, the light emitting diode of the present invention has irregularities on the light emitting surface,
High light extraction efficiency due to having a thin film on the uneven surface,
A light emitting diode with a p-type region arranged above is realized. In addition, according to the manufacturing method of the present invention, a plurality of semiconductor chips can be collectively formed at the same time without forming electrodes, and unevenness and thin film formation can be performed at the same time. Therefore, a light emitting diode can be manufactured at low cost. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a light emitting diode according to the present invention.

FIG. 2 is a process chart showing a manufacturing method of the present invention.

FIG. 3 is a schematic cross-sectional view of an electrode formed on a semiconductor chip.

FIG. 4 is a diagram showing an arrangement state of semiconductor chips after expansion.

FIG. 5 is a cross-sectional electron micrograph of a light emitting diode manufactured by the manufacturing method of the present invention.

FIG. 6 is a cross-sectional electron micrograph of a light emitting diode prepared by the manufacturing method of the present invention.

FIG. 7 is a comparison diagram of the light emission amount of a light emitting diode of the present invention and a light emitting diode formed by a conventional technique.

[Explanation of symbols]

 Reference Signs List 10 light emitting diode 12 n-type semiconductor region 13 p-type semiconductor region 14, 15 electrode 16 pn junction 17 uneven surface 18 thin film 20 semiconductor chip 21 adhesive tape 22 ring

Claims (11)

[Claims] 1. A semiconductor chip in which a p-type first semiconductor region and an n-type second semiconductor region are arranged so as to form a pn junction, and at least a p-type region of the semiconductor chip. And an electrode, and is configured to extract light from a region and a side surface other than the electrode on the upper surface of the semiconductor chip, and the upper surface and / or the side surface of the semiconductor chip other than the electrode have an uneven surface of about 0.5 to 5 μm. A light-emitting diode having a thin film of the compound containing the semiconductor chip material adhered to at least the uneven surface thereof, wherein the upper surface of the semiconductor chip is the p-type first semiconductor region, A light-emitting diode, wherein the side surface is the p-type first semiconductor region and the n-type second semiconductor region. 2. The semiconductor device according to claim 1, wherein the p-type first semiconductor region and the n-type second semiconductor region are formed of a GaAs-based or GaAlAs-based semiconductor material. Light emitting diode. 3. The light-emitting diode according to claim 1, wherein at least the p-type first semiconductor region includes a slope change region having an uneven surface at a side edge thereof. 4. The light emitting diode according to claim 1, wherein said thin film is an arsenic compound containing arsenic hydroxide as a main component. 5. A plurality of semiconductor regions stacked on a semiconductor substrate, wherein at least an n-type second semiconductor region and a p-type first semiconductor region are arranged so as to form a pn junction. A first step of forming individual semiconductor chips; a second step of forming electrodes in at least a p-type region of the semiconductor chip; A third step of adhering a thin film of a compound containing a semiconductor chip material to the uneven surface, the method of manufacturing a light-emitting diode, wherein in the third step, the upper surface region and side surfaces of the semiconductor chip A treatment liquid comprising nitric acid and a water-soluble organic solvent to make the surface irregular, and to attach a thin film of a compound containing a semiconductor chip material to the surface having the irregularity. Method of manufacturing iod. 6. Between the second step and the third step,
An adhesive tape is attached to the back surface of the semiconductor chip, a separation step of cutting each semiconductor chip, and after this separation step, an adhesive tape is extended, and an elongation step of extending the interval between the semiconductor chips is provided. The light emitting device according to claim 5, wherein the third step is performed while the semiconductor chip separated and extended and adhered to the adhesive tape is adhered to the adhesive tape. Diode manufacturing method. 7. The method for manufacturing a light emitting diode according to claim 5, wherein the treatment liquid comprises a mixture of nitric acid and methanol. 8. The method according to claim 5, wherein the third step is performed at a processing liquid temperature of 10 ° C. to 50 ° C. 9. The method according to claim 1, wherein the third step has a processing time of 10 seconds to 5 seconds.
The method for manufacturing a light emitting diode according to claim 5, wherein the method is performed in minutes. 10. The light emitting diode according to claim 5, wherein a mixing ratio of nitric acid and methanol in the treatment liquid is 10: 0.1 to 5 by volume ratio. Method. 11. The method according to claim 5, wherein the water-soluble organic solvent is one of methanol, ethanol, acetone, and isopropyl alcohol.